1. Field of the Invention
This invention relates to a method of preparing di(ketene acetals).
2. Description of the Related Art
Corey et al., J. Org. Chem., 38, 3224 (1973), discloses the isomerization of the allyl ethers of menthol, decanol, and cholesterol to the corresponding 1-propenyl ethers under neutral aprotic conditions catalyzed with tris(triphenylphosphine)rhodium chloride, and the ready hydrolysis of these 1-propenyl ethers to the original alcohols at pH 2.
U.S. Pat. No. 4,304,767 discloses the preparation of a number of di(ketene acetals), such as 3,9-dimethylene-2,4,8,10-tetraoxaspiro[5.5]undecane (the di(ketene acetal) of pentaerythritol), 2,6-dimethylenehexahydrobenzo[1,2-d,4,5-d′]bis[1,3]dioxole (the di(ketene acetal) of 1,2,4,5-cyclohexanetetraol), 1,2-ethylenebis(2-methylene-[1,3]dioxolane] (the di(ketene acetal) of 1,2,5,6-hexanetetraol), and alkylated di(ketene acetals) such as 2,6-diisopropylidenehexahydrobenzo[1,2-d,4,5-d′]bis[1,3]dioxole, 3,9-di-sec-butylidene-2,4,8,10-tetraoxaspiro[5.5]undecane, and 3,9-diisopropylidene-2,4,8,10-tetraoxaspiro[5.5]undecane, by methods which include the isomerization of the di(vinyl acetals); and the preparation of poly(ortho esters) from these and related di- and tri-(ketene acetals) by reaction of the compounds with diols or polyols.
U.S. Pat. No. 4,513,143 discloses the preparation of ketene acetals and di(ketene acetals), such as 3,9-diethylidene-2,4,8,10-tetraoxaspiro[5.5]undecane (DETOSU), by the isomerization of the corresponding di(vinyl acetals) in alkali metal lower n-alkyl/water soluble primary amine solutions.
U.S. Pat. No. 4,532,335 discloses the preparation of ketene acetals and di(ketene acetals), such as DETOSU and 3,9-diisopropylidene-2,4,8,10-tetraoxaspiro[5.5]undecane, by the isomerization of the corresponding di(vinyl acetals) in alkali metal alkoxide/ethyleneamine solutions.
Crivello et al., J. Polymer Sci., Part A: Polymer Chemistry, 34, 3091-3102 (1996), discloses the preparation of a number of ketene acetals and di(ketene acetals), including 2,2′-diethylidene-4,4′-bis-[1,3]dioxolane) and DETOSU, in each case by the preparation of the corresponding di(vinyl acetal) from the relevant tetraol and acrolein and isomerization with tris(triphenylphosphine)-ruthenium dichloride.
German Patent No. 2 331 675 (Chem. Abs., 81:63153v (1974)) discloses the preparation of aliphatic ketene acetals by the isomerization of unsaturated aldehyde acetals having a double bond in the α-, β-, or γ-position of the acetal group with iron carbonyls and/or actinic light. In six examples, 2-vinyl-[1,3]-dioxolane was photoisomerized to methylketene ethylene ketal in the presence of iron pentacarbonyl and N,N-dimethylaniline; diiron nonacarbonyl, N,N-dimethylaniline and hydroquinone monomethyl ether; iron pentacarbonyl and n-octane; and triiron dodecacarbonyl; while acrolein dimethyl acetal was photoisomerized to methylketene dimethyl acetal in the presence of iron pentacarbonyl, and diiron nonacarbonyl.